from radiant to forced air with concrete 'ducts' can CA work?

Hello
This is very difficult to explain so please bear with me.

My house is concrete, basement to roof, including the floors. If I look up at my basement ceiling (which is the floor of the bedroom above) it's concrete. Very cool place, built in the late 1940s. It's one main living floor with a walk-out basement (built on a hill).

I'm told the house was initially built for radiant hot water. I have the original bluleprints but don't really understand them. There are small metal grates where the wall meets the floor on the main level. The grates are built into the concrete and go end-to-end along the front of the house and the back of the house. I assume that's where the original radiant heat water pipes were supposed to be.

The furnace, which is oil forced air, is located in the basement on the right side, and the house is about 35 feet long. There are regular metal vents that go from the furnace to the dining room (which is right above the furnace) and a long, well insulated vent that runs through the garage into the bathroom on the other end of the house. The heat works well coming from both of those vents.

However, they've also apparently fed a vent or something into the voids that run along the front and back of the house, where the radiant heat water pipes were supposed to go. The air that comes out of that is luke warm at best. I cannot see inside them and cannot remove them, but I assume they are not lined with any sort of insulator and are basically just concrete tubes. I'm guessing that the heat just gets mostly absorbed by the concrete and by the time it reaches the rooms that are further away, it's basically pointless.

I've covered the grated sections furthest from the furnace with magnetic material, which helps force the heat to come out about 10-feet sooner in the farthest rooms, which helps a little.

Now, I can live with that (mostly use a wood stove to heat in the winter anyhow) but I'm wondering how a CA will work under those conditions? There is currently an old CA which I had serviced and the tech said I needed a new one. They're very expensive, and, while I'm sure the cool air would come out of the regular metal vents, would it be completely lost in the concrete 'holes.' Given the concrete nature of the house, adding additional vents would be exceptionally expensive, not to mention it could compromise the structural integrity of the place if they hit rebar. If it would only work from the vents, a CA will only be cooling a dining room and a bathroom.

Did Thomas Edison build this house? I thought all of his were in NJ and PA. If you are not aware of these homes, you should get some information them and see if there is an owners' association or something. You might have a lot in common even if yours is not an Edison.

If your area is good for heat pumps, I think you should be looking at heat pump mini splits.